Installing cartr.:slide it all the way to front?

Wow!I am overwhelmed.Thanks guys.I don't even know where to start right now.I've always been a digital guy and had analog on the back burner via a simple Rega 25/Dynavector/CJ EV1 setup.Recently i decided to take it a step further and mounted RB 600 on Michell Gyro SE.I also bought a Shelter 501 II cartridge.I thought that i will install the cartridge by simply using the cadboard template that came with Rega turntable and was more concerned with should i use a 2mm spacer that i used with Dyna cartridge or not.(In my previous post i didn't get a straight answer to that)Now that i asked i feel completely helpless as to where to start.Can you please tell me step by step what to measure first and what to adjust after those measurements.
Let's say the cartridge is already in a head shell sliding back and forth freely.Also what exactly is a pivot point on Rega arm?I feel embarassed by my amateurish questions.
P.S.Word "Overhang" always kinda amused me the same way as actor's name Michael J.Cox amuses in adult movies.

Welcome back Overhang,

First of all, nice new rig! It should play some great music.

If you view the tonearm from directly above and swing the arm back and forth, you can visually imagine the exact point around which it swings. That is the pivot point, the only spot on the arm that DOESN'T move when you swing it.

There's no obvious visual spot at the pivot point on an RB600 so here's what I do: stick a small piece of Scotch tape on top of the arm tube, above the pivot point you just identified. Mark a dot above the pivot point with a pen. Swing the arm a couple of times to confirm the dot isn't moving. If the dot moves, change the position of the tape and try again. When the dot remains stationary you've marked the pivot point. Voila!

Now measure the distance from that point to the center of the TT spindle, in mm. Close counts, + or - 1mm is good enough. Let us know that dimension and we'll go to step 2.

Re: spacers
Once the Shelter is securely mounted and can drop it onto a record you can tell whether you need spacer(s) or not. Shelters typically like to have the cartridge body VERY SLIGHTLY tail-down. Use whatever spacers you need to achieve that orientation.

Thanks Doug.The distance is 216-218 mm.

Raul,
I must have been sleepy. Of course an SME IV/V changes mounting distance when moved on its rack.

In plain 2-D geometry the SME rack is a straight line segment. The TT spindle is a point. Any object moving along a straight line MUST change its distance from a fixed point.

The only path an object can travel without changing distance from a fixed point is a circle with said point at its center.

The SME rack is not a circle or any portion of one. If it were, moving the arm would not alter its relation to the platter or the LP. Such a mechanism would serve no purpose, the arm would literally be going in circles!

Overhang,

AHA! Progress.

It appears your Gyro was used with some arm that needed a shorter mounting distance than a Rega. Fortunately, the Gyro's armboad is adjustable. I don't know the details but there are one or more screws you loosen, after which the mounting plate spins. You'll note the arm mounting hole is offset, so spinning the mounting plate changes the arm's distance from the spindle.

Try to make your spindle-pivot dimension 219-220mm. That's the optimum for a Rega to achieve 2-point Baerwald alignment, which is widely considered the best scheme.

If you can do that, visit www.TurnTableBasics.com and buy their $20 mirrored alignment protractor. The TTB is probably the most accurate protractor short of a $150 WallyTractor. You'll be all set.

Doug

P.S. Don't bother trying to align a cartridge using your Rega protractor with the arm at 216-218mm. It won't be possible. That protractor assumes 223mm. If you don't want to buy the TTB protractor and just want to use the Rega one, you'll have to swivel the arm's pivot point all the way out to 223mm.